This paper focuses on a new granulation study area where a mixture of suspended anaerobic and aerobic cultures was used as seed. Mixed suspended anaerobic and aerobic cultures exposed to alternating anaerobic/microaerobic/aerobic conditions developed granulates up to 2.5 mm in size. The granules developed displayed both oxygen uptake (3.83 - 8.75 mg dissolved oxygen g(-1) volatile suspended solids h(-1)) and methanogenic activities (7.5 cm(3) CH4 d(-1)) comparable to those of aerobic and anaerobic control cultures, respectively. Oxygen doses of 60, 100 and 120% of the total chemical oxygen demand added (23, 38 and 45 cm 3) and ethanol (among ethanol, glucose, acetic acid, and glucose+acetic acid) resulted in the largest and the most stable granules. (c) 2005 Society of Chemical Industry.